Fun concept, but I wish the game did more with having multiple characters across multiple screens.
Maybe some enemies could only be damage by being attacked on two screen at once? A boss that appears on all screens at once, rewarding the player for properly position their four shadows? Level hazards that can only be activated from one screen? I not really a big fan of any of those ideas, but I hope they communicate what I was thinking.
I really only used one screen at a time or ignored them all together. In the beginning, I just found myself focusing on only one screen at a time (as enemies appeared). By the end, I was just jumping around and slashing frantically because that seemed to work well.
I liked the armor mechanic being tied to the weapons because it forced me to pick up weapons I would normally avoid (due to lower stats). The two things that would break me out of my state of jumping and slashing wildly were the coins and weapon drops because I would have to navigate over to them on one screen.